Motion detecting apparatus, motion detecting method and program

Abstract

In a motion detecting apparatus which can perform a high-accuracy motion search with a less calculation cost, it is discriminated whether or not input Activity and DIFF_XORSUM values are smaller than respective predetermined thresholds. If the Activity value is smaller than the threshold or the DIFF_XORSUM value is smaller than the threshold, a reference vector is selected as a motion vector. On the other hand, if the Activity value is equal to or higher than the threshold and the DIFF_XORSUM value is equal to or higher than the threshold, an N-valued image search vector is selected as the motion vector.

What is claimed is: 
     
       1. A motion detecting apparatus comprising:
 a generating unit configured to generate an image which has a number of gradations less than that of an original image of a moving image, wherein the original image has units of blocks; 
 a first motion detecting unit configured to perform motion detection of a target block to detect a motion vector, wherein the motion detection is based on the generated image having the number of gradations less than that of the original image; 
 a calculating unit configured to calculate a flatness value indicating a flatness of the target block, wherein the calculating unit calculates the flatness value using a difference value between (1) an average value of pixel values of the target block in the original image and (2) a pixel value of the target block in the original image; and 
 a selecting unit configured to select, as a motion vector for the target block, (1) a motion vector detected by the motion detection of the target block based on the generated image or (2) a reference motion vector, 
 wherein the selecting unit selects the motion vector detected by the motion detection for the target block based on the generated image as the motion vector for the target block, if the flatness value is not smaller than a first threshold, 
 wherein the selecting unit selects the reference motion vector as the motion vector for the target block, if the flatness value is smaller than the first threshold, wherein the reference motion vector is (a) a zero motion vector or (b) a motion vector based on a motion vector of a block neighboring the target block, and 
 wherein the reference motion vector is a vector independent from the motion detection of the target block based on the generated image. 
 
     
     
       2. The motion detecting apparatus according to  claim 1 , wherein the reference motion vector is a motion vector which is based on motion vectors of blocks neighboring the target block. 
     
     
       3. The motion detecting apparatus according to  claim 1 , wherein the selecting unit performs the selection based on (a) the flatness value indicating the flatness of the target block, and (b) a difference between a first sum of absolute differences and a second sum of absolute differences,
 wherein the first sum of absolute differences is a sum of absolute differences of a block of which a position is pointed by the motion vector based on the detection result, and 
 wherein the second sum of absolute differences is a sum of absolute differences of a block of which a position is pointed by the reference motion vector. 
 
     
     
       4. The motion detecting apparatus according to  claim 3 , wherein the selecting unit selects, as the motion vector for the target block, the motion vector detected by the motion detection of the target block based on the generated image, in a case where the flatness value is not smaller than the first threshold and the difference between the first sum of absolute differences and the second sum of absolute differences is equal to or larger than a second threshold. 
     
     
       5. The motion detecting apparatus according to  claim 3 , further comprising an obtaining unit configured to obtain information indicating movement of an imaging unit which imaged the original image,
 wherein the selecting unit selects, as the motion vector for the target block, the motion vector detected by the motion detection of the target block based on the generated image or the reference motion vector, further based on the information indicating the movement of the imaging unit obtained by the obtaining unit. 
 
     
     
       6. The motion detecting apparatus according to  claim 1 , further comprising a second motion detecting unit configured to perform motion detection based on the original image on the basis of the motion vector selected by the selecting unit. 
     
     
       7. A motion detecting method comprising:
 generating an image which has a number of gradations less than that of an original image of a moving image, wherein the original image has units of blocks; 
 performing motion detection of a target block to detect a motion vector, wherein the motion detection is based on the generated image having the number of gradations less than that of the original image; 
 calculating a flatness value indicating a flatness of the target block, wherein the calculating calculates the flatness value using a difference value between (1) an average value of pixel values of the target block in the original image and (2) a pixel value of the target block in the original image; and 
 selecting, as a motion vector for a target block, (1) a motion vector detected by the motion detection of the target block based on the generated image or (2) a reference motion vector, 
 wherein the selecting selects the motion vector detected by the motion detection for the target block based on the generated image as the motion vector for the target block, if the flatness value is not smaller than a first threshold, 
 wherein the selecting selects the reference motion vector as the motion vector for the target block, if the flatness value is smaller than the first threshold, wherein the reference motion vector is (a) a zero motion vector or (b) a motion vector based on a motion vector of a block neighboring the target block, and 
 wherein the reference motion vector is a vector independent from the motion detection of the target block based on the generated image. 
 
     
     
       8. A non-transitory computer-readable storage medium which stores a program characterized by causing a computer to perform steps comprising:
 a generating step of generating an image which has a number of gradations less than that of an original image of a moving image, wherein the original image has units of blocks; 
 a first motion detecting step of performing motion detection of a target block to detect a motion vector, wherein the motion detection is based on the generated image having the number of gradations less than that of the original image; 
 a calculating step of calculating a flatness value indicating a flatness of the target block, wherein the calculating step calculates the flatness value using a difference value between (1) an average value of pixel values of the target block in the original image and (2) a pixel value of the target block in the original image; and 
 a selecting step of selecting, as a motion vector for the target block, (1) a motion vector detected by the motion detection of the target block based on the generated image or (2) a reference motion vector, 
 wherein the selecting step selects the motion vector detected by the motion detection for the target block based on the generated image as the motion vector for the target block, if the flatness value is not smaller than a first threshold, 
 wherein the selecting step selects the reference motion vector as the motion vector for the target block, if the flatness value is smaller than the first threshold, wherein the reference motion vector is (a) a zero motion vector or (b) a motion vector based on a motion vector of a block neighboring the target block, and 
 wherein the reference motion vector is a vector independent from the motion detection of the target block based on the generated image.